Will buying a 4k TV buy me more trouble?



So I see Walmart has the LG 49UB8200 for $549. (LG 49" 4K TV @ 60 Hz)

Buying that would replace my 52" RCA projection (R52WH74) HDTV. It is a rear projection TV but has been phenomanal in service. I've had to go into the service admin screens a couple of times to align the color emitters but that has not really been any hassle. Especially since I bought it for $380 seven years ago. The reason for ever replacing it would be to free up the space where it sits now. (and if it should break finally)

This is our only TV. We got rid of the other TVs and now just either use tablets or my 23" monitor in another room to watch programs since we've cut cable/sat long ago and now either watch OTA or stream.

Because it is our main TV, I've connected an AV receiver, Blu-ray player and an HTPC (mostly XBMC but browser for HBO Go and other streams not yet configured for XBMC).

- Blu-ray: Samsung BD-H6500
- AV: Pioneer VSX-1120 (HDMI V1.4)
- HTPC: AMD box with AMD Phenom II X6 1090T and Sapphire Radeon HD 6950

So if I buy this 4K TV, I would need a new receiver and a new GPU? I'm not expecting to run 4K stuff right out of the box but I need to know if I won't be able to watch the current stuff (HD, SD) with this configuration.

Any advice?